Yarn Draw-Off Unit of a Rotor Spinning Machine and Method for Producing a Yarn with the Aid of a Rotor Spinning Machine

ABSTRACT

The invention relates to a yarn draw-off unit of a rotor spinning machine, having a draw-off nozzle ( 21 ) which projects into a spinning chamber ( 22 ) of the rotor spinning machine, and a draw-off conduit ( 23 ) for a yarn ( 5 ) produced within the spinning chamber ( 22 ), the draw-off conduit ( 23 ) being arranged downstream of the draw-off nozzle ( 21 ) in the draw-off direction of the yarn ( 5 ) that is drawn off from the spinning chamber ( 22 ). The draw-off conduit ( 23 ) comprises a helical section ( 24 ), with the aid of which a false twist can be imparted to the yarn ( 5 ) within the draw-off conduit ( 23 ). Furthermore, a draw-off nozzle for a rotor spinning machine is described, the draw-off conduit ( 23 ) of which comprises a helical section ( 24 ), with the aid of which a false twist can be imparted to the yarn ( 5 ) within the draw-off nozzle ( 21 ). Finally, the invention relates to a method for producing a yarn ( 5 ) with the aid of a rotor spinning machine. The method is characterised in that the yarn ( 5 ) is exposed to torque within a helical section ( 24 ) of the draw-off conduit ( 23 ), said torque causing the yarn ( 5 ) to rotate about its longitudinal axis, the direction of rotation of the rotation corresponding to the direction of rotation that is imparted to the yarn ( 5 ) by the spinning rotor ( 3 ).

The invention refers to a yarn draw-off unit of a rotor spinning machine that has a draw-off nozzle which projects into a spinning chamber of the rotor spinning machine, and a draw-off conduit for a yarn produced within the spinning chamber arranged downstream of the draw-off nozzle. Furthermore, a method for producing yarn with the help of a spinning position of a rotor spinning machine is suggested in which fiber material consisting of individual fibers is twisted inside a spinning chamber of the spinning position by means of a spinning rotor to become yarn and with the help of a draw-off nozzle, this yarn is drawn out of the spinning chamber through a draw-off conduit. Finally, a draw-off nozzle for a rotor spinning machine with a draw-off conduit is described, through which yarn produced by means of the rotor spinning machine can be drawn off.

Generally speaking, rotor spinning machines are characterized by the fact that the individual fibers of a supplied sliver are introduced individually to a spinning chamber with the help of an opening unit. Inside the spinning chamber, they strike the inner wall of a fast-rotating spinning rotor and the generated centrifugal forces force them to move towards the rotor groove area. The rotation of the spinning rotor finally causes the individual fibers to twist and they, in turn, wind around the end of the already produced yarn (fiber weaving process). In the final analysis, the twisting of individual fibers produces a continuous yarn or the constant lengthening of an already existing yarn that can finally be drawn off the spinning chamber via a draw-off conduit of a corresponding opening unit.

To influence the above-mentioned fiber-weaving process positively, it has already been suggested (see, for example DE 36 09 114 A1) to arrange elevations with the most varied shapes inside the draw-off conduit. Sooner or later, the yarn must pass through these elevations and—owing to their corresponding geometry—a false twist is imparted on the yarn, which opens once again after passing the elevations. The false twist then propagates until it reaches the rotor groove, where it supports the fiber-weaving process by additionally twisting the end of the yarn (to achieve this, the elevations must be arranged in such a way that the false twist generated as a result of this has a twisting direction that corresponds to the one of the already produced yarn).

Even if the elevations mentioned above are quite suitable for positively influencing the fiber-weaving process, the strength of the false twist is basically limited because the elevations for generating the false twist must have a certain “sharp-edged quality” so the yarn can be twisted. If the elevations are too sharp edged, the yarn is subject to excessive mechanical stress and the positive effect of the better fiber integration is neutralized once again by subsequent yarn damage.

The task of this invention is therefore to suggest a draw-off unit/nozzle and a method for producing a yarn in which excessive yarn stress is prevented in spite of good fiber bonding.

The task is solved equipment-wise by a yarn draw-off unit having the characteristics of patent claim 1.

According to the invention, the yarn draw-off unit of the rotor spinning machine is characterized by the fact that the draw-off conduit for the yarn produced in the spinning chamber comprises a helical section with whose help the yarn inside the draw-off conduit can be provided with a false twist. In this case, the produced yarn gets the desired false twist by its helically restricted guidance or the torsion moment created as a result of this acting on the yarn while it passes through the above-mentioned section. In the final analysis, the finished yarn gets a twist, which in turn exerts the desired torque on the end of the yarn in the spinning rotor groove area placed downstream. The basic idea behind the invention is therefore to guide the yarn through a helical draw-off conduit. Generally, such a section has no transitional (sharp) edges so that an excessive mechanical stress of the yarn can be ruled out too. Rather, the yarn is carefully guided on a helical track that allows the yarn to be guided especially gently while allowing a false twist. In other words, the yarn passes appropriately through a conduit closed on ail sides with a preferably round or oval cross-section that is part of the draw-off conduit and takes a helical course.

An advantageous further development foresees that the helical section is limited by the surface section of an insert. Whereas the helical section of the draw-off conduit can also pass inside the corresponding structural part, surface treatment is associated with considerable lower production costs. The corresponding section can in this case be milled into the surface of the insert, which has preferably a cylindrical external contour that is interrupted merely by the course of the draw-off conduit's helical section.

It is especially advantageous if a wall surrounds the insert and the insert's surface section facing the wall has a helical and preferably groove-shaped depression that forms the helical section together with the neighboring part of the wall. In this case, the insert is not required to have an internal conduit. Rather, the section of the draw-off conduit according to the invention is created by the combined action of a surface section of the insert (in form of limiting surfaces of the depression) and the hereby corresponding opposite surfaces of the wall adjacent to the insert of a structural part of the rotor spinning machine that carries the insert. The depressions can be easily built in using material-removing methods in a basic cylindrical body, for example, while the structural part containing the finished insert and the wall mentioned above does not have to be processed at all with regard to the creation of the helical draw-off conduit.

It is therefore generally advantageous if the insert and a structural part of the yarn draw-off unit in the wall to be made from separate materials. Both units can in this case be made from different materials; the insert especially of ceramic, metal or plastic. Finally, the insert can be glued or screwed onto the structural part having the wall (e.g. the lid of the rotor unit or the draw-off nozzle). Even a pressing against one another is conceivable, in which case the insert should by all means be arranged in a stationary way with respect to the walled structure.

It is additionally advantageous if the walled structural part is tubular and the insert inside the tube is arranged in a stationary way with respect to the tube. Thus, the tube represents another structural part that serves above all for the insert's placement and therefore also for limiting the helical section of the draw-off conduit according to the invention. The tube itself can, in turn, be arranged in the lid's bore hole/opening of the housing that limits the spinning chamber.

In this context, it is particularly advantageous if the insert is glued to the tube, but purely form-fitting joints are conceivable too (threaded joints, pressing).

It is especially advantageous if the tube connects the draw-off nozzle with a draw-off pipe, in which case the insert is placed between draw-off nozzle and draw-off pipe and surrounded by the tube. Here, the tube serves for arranging the insert and the draw-off nozzle and thus ensures that the draw-off conduit runs perfectly positioned from the yarn intake of the draw-off nozzle to the draw-off pipe. In addition, the tube is preferably rotationally circular and has one or several stop surfaces on which the draw-off nozzle and/or draw-off pipe fits tightly or with whose help the tube itself comes to rest on the correspondingly neighboring structural part of the rotor spinning machine.

It is furthermore also advantageous if the tube is in operational contact with a driving element and can be made to rotate with the help of this driving element. The helical section of the draw-off conduit according to the invention can in this case be driven, whereby the rotational direction either matches the rotational direction of the spinning rotor or can be oriented in opposite direction to it. In the final analysis, thanks to the additional rotational movement of the above-mentioned section, the yarn structure can be improved and the rotation has an especially positive effect on the optical uniformity of the yarn. The tube's possible speed should lie preferably within a range of 10,000 rpm to 100,000 rpm. Especially preferable is a range between 20,000 rpm and 60,000 rpm, but the best results could be achieved with a speed of 30,000 to 50,000 rpm. The propulsion of the tube takes place preferably with the help of a driving belt slung around the tube that, in turn, can be in operational contact with a corresponding drive (e.g. an electrical motor or a central motor shaft of the rotor spinning machine).

In this context, it can be advantageous if the tube is mounted above a pivot bearing and made to rotate relative to the draw-off tube fixed in place. In other words, it can be advantageous if the draw-off nozzle does not rotate while yarn is being produced, while the section of the draw-off conduit according to the invention is made to rotate in the way mentioned above. In this case, a pivot bearing can be placed between draw-off nozzle or a structural part of the yarn draw-off unit holding the draw-off nozzle and the tube that—in spite of possible relative movement between draw-off nozzle and tube—prevents air from escaping from or entering into the draw-off conduit. It is particularly advantageous if the tube is rotationally mounted in the area of its two front sides to ensure stable mounting.

If can also be advantageous if the tube is connected with the draw-off nozzle in a non-rotatable way, so that the draw-off nozzle can be made to rotate together with the tube. It is therefore conceivable to prevent a relative movement between the tube and the spinning nozzle so that the yarn produced strikes a moving surface already in the spinning nozzle area. In this case, tube and spinning nozzle can be glued together, for example. Alternately, it is also conceivable to provide another structural part to connect the tube to the spinning nozzle in a non-rotatable way between tube and spinning nozzle.

It is additionally advantageous if the insert, on its side facing the draw-off nozzle, has an inlet bevel that ends in the guiding conduit and/or has, on its side facing away from the draw-off nozzle, an outlet bevel to extend the guiding conduit. In this case, when the yarn passes a straight section of the draw-off conduit towards the helical section its course is not suddenly diverted, but experiences a gentle guiding into or out of the draw-off conduit section according to the invention.

It is also advantageous if the inlet bevel and/or outlet bevel end flush in the adjacent area of the draw-off conduit. Stepped or sharp-edged transitions are fully prevented in this embodiment, so that the yarn can be guided especially gently. The bevels mentioned above are preferably formed by the insert's corresponding sections, which can be placed on the respective front sides of it.

It is furthermore advantageous if the insert is placed at least partially inside the draw-off nozzle. Thus, the insert can be an integral part of the draw-off nozzle, which in this case can be exchanged together with the insert. Finally, a draw-off nozzle is obtained that already has the draw-off conduit section according to the invention, so that this draw-off nozzle can also be used in already existing rotor spinning machines without the need of further constructive interventions.

It is especially advantageous if a straight section of the draw-off conduit is arranged between a yarn inlet of the draw-off nozzle and the helical section. In this case, the draw-off nozzle can have a (centric) bore hole and is therefore easily manufactured. This bore hole is finally followed by the insert, which in turn makes available a part of the limiting surfaces of the draw-off conduit's helical section.

It is furthermore advantageous if the insert is made of ceramic, metal or plastic. The insert can also be cast or made by (surface) treating a base body. Likewise conceivable are various insert coatings or especially its surface areas making contact with yarn so the friction between insert and yarn can be correspondingly adjusted.

It is additionally advantageous if the helical guidance device has a number of turns between 0.2 and 5, preferably between 1 and 3. While a high number causes the yarn to twist very strongly, a low number causes only a low torsion moment on the yarn, so that the outer fibers of the yarn are exposed to only slight mechanical stress. Even if the guidance device can only have one-half of a turn, for example, it is nonetheless a helical contact surface for the yarn, i.e. the contact surface has a bent section and also extends in longitudinal direction of the remaining draw-off conduit, thus finally creating a helical course.

It is advantageous if—seen from the top—the helical section describes a circular arch that, with respect to a longitudinal axis of the draw-off conduit, has a middle point angle α that is at least 60°, preferably at least 120° and especially preferably at least 180°. The section according to the invention can therefore, as pointed out above, have less than a full turn and yet the bent shape nonetheless ensures that a corresponding false twist can be imparted.

It can finally be advantageous if the insert is made up of several, preferably equal individual elements, in which case the individual elements are joined with one another in a force- or form-fitting way. In other words, a “basic helix” is used that is designed in such a way that it can be joined with other additional basic helices in a force- or form-fitting way. In the final analysis, this creates the possibility of varying the length of the insert or number of turns of the draw-off conduit by the number of individual elements joined to one another. Here, the individual elements can have, for example, one or several depressions on one of their front sides and one or several extensions on the opposite front side. If two individual elements are joined together, then the extension(s) of the one individual element grip(s) the depression(s) of the adjacent individual element. The extension(s) or depression(s) have preferably, in at least one area, a non-circular cross section so that the individual elements joined together cannot be twisted against one another. This means that a smooth draw-off conduit can be formed from the individual elements joined together that extends along the entire individual element. Moreover, it is possible for the insert to be made of one or several identical middle pieces, in which case the starting piece has an inlet bevel and the terminal piece an outlet bevel. The number of middle pieces determines finally the overall length of the insert (although it is possible to dispense with the middle piece). Finally, the insert can be made up of several identical individual elements that in each case have one inlet bevel and one outlet bevel. The contours of the inlet and outlet bevel are preferably coordinated in such a way that they create a tight fit when the individual elements are joined together and ensure the rotation prevention mentioned above.

The draw-off nozzle according to the invention has a draw-off conduit with a helical section used to help the yarn be imparted a false twist inside the draw-off nozzle. In other words, the draw-off nozzle itself has the section according to the invention. Thus, any already existing rotor spinning machine equipped with separate draw-off nozzles can be subsequently equipped with a draw-off nozzle according to the invention in order to improve yarn quality, particularly the fiber bonding process. The section according to the invention can in this case be formed by an insert too, as already described above, in which case the draw-off nozzle has preferably a cylindrical bore hole in which the insert is introduced and fixed in place (by gluing it for example).

Finally, the method according to the invention for producing yarn with the help of a spinning position of a rotor spinning machine is characterized by the fact that the yarn is exposed to a torsion moment inside the helical section of the draw-off conduit that causes the yarn to twist around its longitudinal axis, in which case the twisting direction corresponds to the twist of the twisting direction that the yarn received from the spinning rotor. Here, the draw-off unit or spinning nozzle described so far can be especially used. With regard to the respective individual elements, which can be used in any combination, reference is made to the description given above or below. In particular, it is also foreseen that the generated twist of the yarn in the draw-off conduit area is generated by the yarn making contact with the wall of the helical section of the draw-off conduit. A preferred embodiment of the method foresees the yarn to be guided along a helical path around an insert. In this case, the yarn is effectively guided through a helical, groove-shaped depression running above the surface of the insert.

Further advantages of the invention are described in the following embodiments, which show:

FIG. 1 a partially cut side view of a known rotor spinning machine,

FIG. 2 a partially cut detailed view of a spinning chamber of a rotor spinning machine according to state of the art,

FIG. 3 a partially cut side view of a draw-off nozzle according to the invention,

FIG. 4 a partially cut side view of a draw-off unit according to the invention,

FIG. 5 a partially cut side view of an additional draw-off unit according to the invention,

FIG. 6 a side and top view of a middle piece of a multipart insert for a draw-off unit according to the invention, and

FIG. 7 a partially cut view of an additional draw-off unit,

FIG. 1 shows a partially cut side view of a known rotor spinning machine that generally comprises numerous spinning positions 1 arranged beside one another in the longitudinal direction of the machine (i.e. perpendicular to the drawing plane). From a spinning can 3, fiber material 2 is fed to each spinning position 1 in a known way by means of a supply device 11 and the fiber material 2 is opened to become individual fibers with the help of an opening roller 10 and fed to a spinning rotor 4 through a fiber supply conduit 16 to a fiber feeding conduit 16 indicated by broken lines in FIG. 2 (with respect to the sheet plane, coming from behind). The yarn 5 produced in the spinning rotor 4 is finally drawn off the spinning position 1 via an exit 13 through a draw-off device 7 that comprises, for example, a draw-off roller pair 6, possibly inspected for yarn mistakes by a yarn monitoring unit 12 and wound up with a spool device 8 that includes a spool 9.

As can be seen in the detailed view of FIG. 2, the spinning position 1 has a spinning chamber 22 into which the spinning rotor 4 driven by a rotor shaft 20 projects and that is limited by a housing 18 and a lid 17 that can be swiveled away. Between lid 17 and housing 18, there is generally a gasket 19 to maintain the negative pressure inside the spinning chamber 22.

Finally, the draw-off of the produced yarn 5 takes place through a so-called draw-off nozzle 21 (or its yarn inlet 15), which can be detachably anchored on the lid 17 in form of an insert, for example, and that is connected most of the time to a draw-off pipe 14 that is also mounted on the lid 17 with the help of a carrier 34, for example. The inner conduits of the draw-off nozzle 21, of the carrier 34 and of the draw-off pipe 14 finally form a draw-off conduit 23 that ensures the necessary guidance of the yarn 5 when it is drawn off the spinning chamber 22.

Generally, during rotor spinning, the fibers—now individual (not shown) after passing through the opening roller 10—are suctioned into the spinning rotor 4 and forced by the high rotational speed of the spinning rotor 4 into its inner groove 35, where they make contact with the yarn 5 indicated in FIG. 2 and, owing to the rotor's rotation, are slung around its likewise rotating end (so-called fiber bonding process). In this way, yarn 5 that can be drawn off through the drawn-off nozzle 21 is produced continuously.

To improve the fiber bonding process even more, it was already suggested to place more or less sharp deviations (i.e. convexities of the draw-off conduit wall) within the draw-off conduit 23. The deviations apply a torsion moment to the finished yarn 5 that causes the yarn 5 to get a false twist (i.e. a twist that reopens after it passes the deviations). The false twist eventually propagates through the draw-off nozzle 21 ail the way to the groove 35 of the spinning rotor 4, in the final analysis supporting the fiber bonding on the corresponding end of the already spun yarn 5.

Although the design of the deviations can influence the strength of the false twist, especially sharp deviations (those that would impart a strong false twist) lead to an excessive mechanical stress of the yarn 5 and ultimately limit the strength of the false twist.

To counteract this problem, the invention suggests the draw-off conduit 23 to comprise a helical section 24 for the yarn 5 with whose help a false twist can be imparted on the yarn 5 inside the draw-off conduit 23.

FIG. 3 shows a draw-off nozzle 21 according to the invention, whereby the helical section 24 according to the invention is formed by an insert 25 placed inside the draw-off conduit 23 of a (generally circular) draw-off nozzle 21, as can also be used in principle in the rotor spinning machine in accordance with FIG. 2.

The insert 25—which can be glued to the draw-off conduit 23, for example—has a basically cylindrical outer structure corresponding to the inner contour of the wall 27 limiting the opening of the spinning nozzle. Furthermore, on an adjacent surface section 26 of the wall 27 mentioned above, it has a helical depression 28 that winds around the surface of the insert 25 in the manner of a helical line. The preferably groove-shaped depression 28 is limited externally by the part 29 of the wall 27 adjacent to the depression 28.

In the final analysis, a draw-off conduit 23 with a helical section 24 is obtained through which the yarn 5 must pass when it comes out of the spinning chamber during the draw-off process 22. If the twisting of the helical shape is aligned in one direction corresponding to the twisting direction of the yarn 5 entering the yarn inlet 15, the twisting is strengthened in the area of the insert 25, The corresponding false twist (which opens once again after the insert 25) finally propagates all the way to the groove of the spinning rotor 4, where it causes a highly reliable fiber bonding on the end of the yarn 5, and there is hardly any extra mechanical stress while the false twist is generated due to the rounded off limiting areas of the helical section 24.

The number or slope of the windings shown should be understood as merely exemplary. Naturally, taking relevant additional magnitudes into account (type of draw-off nozzle 21, yarn 5 to be spun, rotor speed, etc.), both parameters can be adjusted and deviate slightly or greatly from the values shown. The draw-off nozzle 21 does not have to be, in principle, an individual part detachable from the lid 17. Rather, as part of this invention, the term “draw-off nozzle” is understood to be generally that section of the spinning device that extends into the spinning rotor 4 and comprises the draw-off conduit 23 that follows the yarn inlet 15.

Finally, FIG. 4 shows a yarn draw-off unit according to the invention in which the section 24 of the draw-off conduit 23 running helically and limited by the insert 25 is not arranged inside the draw-off nozzle 21, but after it. In this case, the insert 25 is mounted inside a tube 30, which in turn connects the draw-off nozzle 21 with a draw-off pipe 14. Thus, one gets a replaceable unit if necessary that can simply be exchanged when it has worn off.

To minimize further the mechanical stress of the drawn-off yarn 5 during its twisting inside the helical section 24, it can finally be advantageous if the insert 25—as shown in FIGS. 3 and 4—has an inlet bevel 31 and/or an outlet bevel 32 to prevent sharp-edged deviations so the yarn 5 is led especially gently into and out of the insert 25. While the inlet bevel 31 could be located right after the yarn inlet 15 (see especially FIG. 3), it has also proven to be very favorable if the draw-off conduit 23 has a straight section 33 between the yarn inlet 15 and the helical section 24. Conventional draw-off nozzles 21 can be especially used in this case that could be supplemented with an insert 25 according to the invention.

It can furthermore be advantageous to build the insert 25 from multiple parts. FIGS. 5 and 6, for example, show a corresponding embodiment.

As can be seen in these figures, the insert 25 shown consists of a starting piece 37 having the inlet bevel 31, a terminal piece 38 having the outlet bevel 32 and a middle piece 36 arranged in between. In their built-in state, the starting piece 36, middle piece 37 and terminal piece 38 have contact surfaces 39 correspondingly abutting one another as well as form-fittingly interlocking rotation preventers.

As can be seen in FIG. 6, rotation prevention can be achieved if the corresponding extensions 40 and the respective depressions 41 act together. For example, the middle piece 36 has an extension 40 in the area of one of its two front sides and a corresponding depression 41 in the area of the opposite front side. If the starting piece 37 shown in FIG. 5 has likewise a corresponding depression 42 in its right front side, then the middle piece 36 can be put together with the starting piece 37 in a form-fitting way through its extension 40. A corresponding connection is also possible with the terminal piece 38 if it has a corresponding extension 40 that matches the depression 41 of the middle piece 36 on its contact surface 39 facing the middle piece 36.

The advantage of a multipart insert 25 is finally that the number of used middle pieces 36 can vary depending on the respective process parameters (fiber material 2 to be spun, spinning speed, etc.). If the terminal piece 38 is coupled directly with the starting piece 37, then one gets an especially short draw-off conduit 23, while it can be lengthened by the respective in-between arrangement of one or several middle pieces 36.

Naturally, it is also possible to design starting piece 37, terminal piece 38 and middle piece 36 identically, so that the corresponding inserts 25 can, in turn, be put together from a uniform basic element. In particular, it would be conceivable in this context for every one of the basic elements to have one inlet bevel 31 and one outlet bevel 32 (comparable to the insert 25 in FIG. 4), in which case inlet bevel 31 and outlet bevel 32 are placed contiguously next to two adjacent mounted basic elements so a mutual twisting is ruled out and a continuous draw-off conduit 23 is created.

Finally, FIG. 7 shows an advantageous embodiment of the invention in which the structural part that has the helical section 24 can be actively driven. The structural part mentioned can be, for example, a tube 30 in whose interior a section 24 according to the invention has an insert 25 according to one of the FIGS. 4 to 6.

To drive the structural part, it can be, in turn, connected preferably via a driving belt 44 shown partially cut in FIG. 7 to a driving axis 45, which, in turn, can be made to execute a twisting movement by a drive (an electric motor, for example, not shown). For this, the structural part (in FIG. 7, the tube 30) and the driving axis 45 should have a circular external contour in a cut running perpendicularly to the drawing plane so that the structural part and the driving axis 45 can be slung and made to twist by the driving belt 44 that is under tension.

In this context, it is for example conceivable to design the tube 30 with the front section 42 shown and/or the back section 43 shown to consist of one single part so the two sections 42, 43 can be made to rotate (and also the draw-off nozzle 21 if the front section 42 and the draw-off nozzle 21 are correspondingly joined). Alternatively, it would also be conceivable to mount the tube 30 through corresponding pivot bearings inside the respective fixed sections (front section 42, back section 43 and other available carrier elements) so that the tube 30 can still be driven if the draw-off nozzle 21 is not moving.

This invention is not limited to the embodiment shown and described. Variations within the framework of the patent claims are just as possible as a combination of the characteristics, even if they are shown and described in different embodiments.

LIST OF REFERENCE CHARACTERS

-   1 Spinning position -   2 Fiber material -   3 Spinning can -   4 Spinning rotor -   5 Yarn -   6 Draw-off roller pair -   7 Draw-off device -   8 Spool device -   9 Spool -   10 Opening roller -   11 Supply device -   12 Yarn monitoring unit -   13 Exit -   14 Draw-off pipe -   15 Yarn inlet -   16 Fiber feeding conduit -   17 Lid -   18 Housing -   19 Gasket -   20 Rotor shaft -   21 Draw-off nozzle -   22 Spinning chamber -   23 Draw-off conduit -   24 Helical section of the draw-off conduit -   25 Insert -   26 Surface section of the insert -   27 Wall -   28 Helical depression -   29 The wall part adjacent to the depression -   30 Tube -   31 Inlet bevel -   32 Outlet bevel -   33 Straight section of the draw-off conduit -   34 Carrier -   35 Groove -   36 Middle piece -   37 Starting piece -   38 Terminal piece -   39 Contact surface -   40 Extension -   41 Depression -   42 Front section -   43 Back section -   44 Driving belt -   45 Driving axis 

1. Yarn draw-off unit of a rotor spinning machine that has a draw-off nozzle (21) projecting into a spinning chamber (22) of the rotor spinning machine, and a draw-off conduit (23) for yarn (5) produced inside the spinning chamber (22), wherein the draw-off conduit (23) is arranged downstream of the draw-off nozzle (21) in the draw-off direction of the yarn (5) that is drawn off from the spinning chamber (22), characterized in that the draw-off conduit (23) has a helical section (24) with whose help a false twist can be imparted to the yarn (5) inside the draw-off conduit (23). 2-20. (canceled) 